Structure and method for SRAM FinFET device

ABSTRACT

The present disclosure provides an embodiment of a fin-like field-effect transistor (FinFET) device. The device includes a first fin structure disposed over an n-type FinFET (NFET) region of a substrate. The first fin structure includes a silicon (Si) layer, a silicon germanium oxide (SiGeO) layer disposed over the silicon layer and a germanium (Ge) feature disposed over the SiGeO layer. The device also includes a second fin structure over the substrate in a p-type FinFET (PFET) region. The second fin structure includes the silicon (Si) layer, a recessed silicon germanium oxide (SiGeO) layer disposed over the silicon layer, an epitaxial silicon germanium (SiGe) layer disposed over the recessed SiGeO layer and the germanium (Ge) feature disposed over the epitaxial SiGe layer.

PRIORITY DATA

This application is a continuation application of U.S. patentapplication Ser. No. 14/953,768, filed Nov. 30, 2015, now U.S. Pat. No.10,453,961, issued Oct. 22, 2019, which is a divisional application ofU.S. patent application Ser. No. 14/317,907, filed Jun. 27, 2014, nowU.S. Pat. No. 9,224,736, issued Dec. 29, 2015, which is related topatent application U.S. Ser. No. 13/740,373 filed on Jan. 14, 2013, as“Semiconductor Device and Fabricating the Same”, now U.S. Pat. No.8,901,607, issued Dec. 2, 2014; U.S. Ser. No. 13/902,322 filed on May24, 2013, as “FinFET Device and Method of Fabricating Same”, now U.S.Pat. No. 9,318,606, issued Apr. 19, 2016; U.S. Ser. No. 13/934,992 filedon Jul. 3, 2013, as “Fin Structure of Semiconductor Device”, now U.S.Pat. No. 9,006,786, issued Apr. 14, 2015; U.S. Ser. No. 14/155,793 filedon Jan. 15, 2014, as “Semiconductor Device and Formation Thereof”, nowU.S. Pat. No. 9,257,559, issued Feb. 9, 2016; U.S. Ser. No. 14/254,072filed on Apr. 16, 2014, as “A Method and Structure for FinFET Device”,now U.S. Pat. No. 9,209,185, issued Dec. 8, 2015 and U.S. Ser. No.14/254,035 filed on Apr. 16, 2014, as “FinFET Device With High-K MetalGate Stack”, the entire disclosures of which are hereby incorporated byreference.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experiencedexponential growth. Technological advances in IC materials and designhave produced generations of ICs where each generation has smaller andmore complex circuits than the previous generation. In the course of ICevolution, functional density (i.e., the number of interconnecteddevices per chip area) has generally increased while geometry size(i.e., the smallest component (or line) that can be created using afabrication process) has decreased. This scaling down process generallyprovides benefits by increasing production efficiency and loweringassociated costs.

Such scaling down has also increased the complexity of processing andmanufacturing ICs and, for these advances to be realized, similardevelopments in IC processing and manufacturing are needed. For example,a three dimensional transistor, such as a fin-like field-effecttransistor (FinFET), has been introduced to replace a planar transistor.Although existing FinFET devices and methods of fabricating FinFETdevices have been generally adequate for their intended purposes, theyhave not been entirely satisfactory in all respects.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read in association with the accompanyingfigures. It is noted that, in accordance with the standard practice inthe industry, various features in drawings are not drawn to scale. Infact, the dimensions of illustrated features may be arbitrarilyincreased or decreased for clarity of discussion.

FIG. 1 is a flow chart of an example method for fabricating a FinFETdevice in accordance with some embodiments.

FIG. 2 is a diagrammatic perspective view of an example FinFET deviceundergoing processes in accordance with some embodiments.

FIGS. 3A-3B, 4A-4B, 5A-5B, and 6A-6B are diagrammatic perspective viewsof an example FinFET device at fabrication stages constructed accordingto the method of FIG. 1 .

FIG. 7A is a cross-sectional view of an example FinFET device alone theline A-A in FIG. 6A at fabrication stages constructed according to themethod of FIG. 1 .

FIG. 7B is a cross-sectional view of an example FinFET device alone theline B-B in FIG. 6B at fabrication stages constructed according to themethod of FIG. 1 .

FIGS. 7C-7D, 8A-8B, 9A-9B, 10A-10B and 11A-11B are diagrammaticperspective views of a FinFET device undergoing processes in accordancewith some embodiments.

FIG. 11C is a cross-sectional view of an example FinFET device along theline A-A in FIG. 11A at fabrication stages constructed according to themethod of FIG. 1 .

FIG. 11D is a cross-sectional view of an example FinFET device along theline AA-AA in FIG. 11A at fabrication stages constructed according tothe method of FIG. 1 .

FIG. 11E is a cross-sectional view of an example FinFET device along theline B-B in FIG. 11B at fabrication stages constructed according to themethod of FIG. 1 .

FIG. 11F is a cross-sectional view of an example FinFET device along theline BB-BB in FIG. 11B at fabrication stages constructed according tothe method of FIG. 1 .

FIG. 12 is another flow chart of an example method for fabricating aFinFET device in accordance with some embodiments.

FIGS. 13A-13B, 14A-14B, 15A-15B, 16A-16B, 17A-17B and 18A-18B arediagrammatic perspective views of a FinFET device undergoing processesin accordance with some embodiments.

FIG. 18C is a cross-sectional view of an example FinFET device along theline B-B in FIG. 18B at fabrication stages constructed according to themethod of FIG. 12 .

FIG. 18D is a cross-sectional view of an example FinFET device along theline BB-BB in FIG. 18B at fabrication stages constructed according tothe method of FIG. 12 .

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

The present disclosure is directed to, but not otherwise limited to, afin-like field-effect transistor (FinFET) device. The FinFET device, forexample, may be a complementary metal-oxide-semiconductor (CMOS) deviceincluding a P-type metal-oxide-semiconductor (PMOS) FinFET device and anN-type metal-oxide-semiconductor (NMOS) FinFET device. The followingdisclosure will continue with a FinFET example to illustrate variousembodiments of the present invention. It is understood, however, thatthe application should not be limited to a particular type of device,except as specifically claimed.

FIG. 1 is a flowchart of a method 1000 for fabricating a FinFET device200 in accordance with some embodiments. It is understood thatadditional steps may be implemented before, during, and after themethod, and some of the steps described may be replaced or eliminatedfor other embodiments of the method. The FinFET device 200 and themethod 1000 making the same are collectively described with reference tovarious figures.

Referring to FIGS. 1 and 2 , the method 1000 begins at step 1002 byproviding a substrate 210. The substrate 210 may include a bulk siliconsubstrate. Alternatively, the substrate 210 may include an elementarysemiconductor, such as silicon or germanium in a crystalline structure;a compound semiconductor, such as silicon germanium, silicon carbide,gallium arsenic, gallium phosphide, indium phosphide, indium arsenide,and/or indium antimonide; or combinations thereof.

In another embodiment, the substrate 210 has a silicon-on-insulator(SOI) structure with an insulator layer in the substrate. An exemplaryinsulator layer may be a buried oxide layer (BOX). The SOI substrate maybe fabricated using separation by implantation of oxygen (SIMOX), waferbonding, and/or other suitable methods.

In the present embodiment, the substrate 210 includes a firstsemiconductor material layer 212, a second semiconductor material layer214 disposed over the first semiconductor material layer 212 and a thirdsemiconductor material layer 216 disposed over the second semiconductormaterial layer 214. The second and third semiconductor material layers,214 and 216, are different from each other. The second semiconductormaterial layer 214 has a first lattice constant and the thirdsemiconductor material layer 216 has a second lattice constant differentfrom the first lattice constant. In the present embodiment, the secondsemiconductor material layer 214 includes silicon germanium (SiGe), andboth of the first and the third semiconductor material layers, 212 and216, include silicon (Si). In various examples, the first, the secondand the third semiconductor material layers, 212, 214 and 216, mayinclude germanium (Ge), silicon (Si), gallium arsenide (GaAs), aluminumgallium arsenide (AlGaAs), silicon germanium (SiGe), gallium arsenidephosphide (GaAsP), or other suitable materials. In the presentembodiment, the second and the third semiconductor material layers, 214and 216, are deposited by epitaxial growth, referred to as a blanketchannel epi. In various examples, the epitaxial processes include CVDdeposition techniques (e.g., vapor-phase epitaxy (VPE) and/or ultra-highvacuum CVD (UHV-CVD)), molecular beam epitaxy, and/or other suitableprocesses.

Referring again to FIGS. 1 and 2 , the method 1000 proceeds to step 1004by forming first fin structures 220 and trenches 230 in the substrate210. In one embodiment, a patterned fin hard mask (FHM) layer 222 isformed over the substrate 210. The patterned FHM layer 222 includessilicon oxide, silicon nitride, silicon oxynitride, or any othersuitable dielectric material. The patterned hard mask layer 222 mayinclude a single material layer or multiple material layers. Thepatterned FHM layer 222 may be formed by depositing a material layer bythermal oxidation, chemical vapor deposition (CVD), atomic layerdeposition (ALD), or any other appropriate method, forming a patternedphotoresist (resist) layer by a lithography process, and etching thematerial layer through the openings of the patterned photoresist layerto form the patterned FHM layer 222.

The substrate 210 is then etched through the patterned FHM layer 222 toform the first fin structures 220 and the trenches 230 in the substrate210. In another embodiment, the patterned photoresist layer is directlyused the patterned FHM layer 222 as an etch mask of the etch process toform the first fin structures 220 and the trenches 230 in the substrate210. The etching process may include a wet etch or a dry etch. In oneembodiment, the wet etching solution includes a tetramethylammoniumhydroxide (TMAH), a HF/HNO₃/CH₃COOH solution, or other suitablesolution.

In the present embodiment, the etching depth is controlled such that thethird and the second semiconductor material layers, 216 and 214 areexposed while a portion of the first semiconductor material layer 212 isexposed in the trench 230. Thus the first fin structure 220 is formed tohave the third semiconductor material layer 216 as its upper portion,the second semiconductor material layer 214 as its middle portion andthe first semiconductor material layer 212 as its bottom portion.

The previous discussion with respect to FIGS. 1 and 2 applies to amethod of manufacturing either an n-type FinFET (NFET) device and/or ap-type FinFET (PFET) device. The process described below, discusses theprocess of manufacturing either an NFET device and/or a PFET device. Insome embodiment, the FinFET device 200 includes an NFET device,designated with the reference numeral 200A and referred to as the NFETdevice 200A. The FinFET device 200 also includes a PFET device,designated with the reference numeral 200B and referred to as the PFETdevice 200B.

Referring to FIGS. 1 and 3A-3B, the method 1000 proceeds to step 1006 byconverting the second semiconductor material layer 214 in the NFETdevice 200A into a semiconductor oxide layer 324. In one embodiment,first a patterned oxidation-hard-mask (OHM) 310 is formed over thesubstrate 210, including wrapping a portion of the first fin structures220. The patterned OHM 310 covers the PFET 200B while leaving the NFETdevice 200A being un-covered during the step of converting the secondsemiconductor material layer 214 in the NFET device 200A into thesemiconductor oxide layer 324.

The patterned OHM layer 310 may include silicon oxide, silicon nitride,silicon oxynitride, or any other suitable dielectric material. Thepatterned OHM layer 310 may be formed by depositing a material layer bythermal oxidation, chemical CVD, ALD, or any other appropriate method,forming a patterned photoresist (resist) layer by a lithography process,and etching the material layer through the openings of the patternedphotoresist layer to form the patterned OHM layer 310.

In the present embodiment, a thermal oxidation process is performed toconvert the second semiconductor material layer 214 in the NFET device200A to the semiconductor oxide layer 324. In one embodiment, thethermal oxidation process is conducted in oxygen ambient. In anotherembodiment, the thermal oxidation process is conducted in a combinationof steam ambient and oxygen ambient. In one embodiment, the thermaloxidation process is controlled such that the second semiconductormaterial layer 214 oxidizes much faster that the first and thirdsemiconductor material layers, 212 and 216. Therefore outer layers ofthe first and third semiconductor material layers, 212 and 216 oxidizedare quite thin. After the oxidation process, a cleaning process isperformed to remove the oxidized outer layers of the first and thirdsemiconductor layers, 212 and 216. The cleaning process may be performedusing diluted hydrofluoric (DHF) acid.

After the thermal oxidation process, the first fin structures 220 in theNFET device 200A have different structures than those in the PFET device200B. For the sake of clarity to better description, the first finstructure 220 in the NFET device 200A is referred to as a second finstructure 330. Thus the second fin structure 330 has the thirdsemiconductor material layer 216 as its upper portion, the semiconductoroxide layer 324 as its middle portion and the first semiconductormaterial layer 212 as its bottom portion. The semiconductor oxide layer324 applies an adequate stress to the third semiconductor material layer216 in the second fin structure 330, where a gate channel is to bedefined underlying a gate region, which will be described later.

In one embodiment, the second semiconductor material layer 214 includessilicon germanium (SiGe), the semiconductor oxide layer 324 includessilicon germanium oxide (SiGeO) and both of the first and the thirdsemiconductor material layers, 212 and 216, include silicon (Si).

In an alternative embodiment, the formation of the OHM 310 is skippedduring step 1006 and the first fin structures 220 in the NFET device200A and the PFET device 200B are exposed in the thermal oxidation. Thesecond semiconductor material layer 214 of the first fin structures 220in both of the NFET device 200A and the PFET device 200B are convertedto the semiconductor oxide layer 324.

The following description will be directed to the embodiment, which hasthe semiconductor oxide layer 324 in the NFET device 200A only. Thoseskilled in the art should also recognize that the method 1000 wouldsimilarly apply to various embodiments, such as the embodiment, whichhas the semiconductor oxide layer 324 in both of the NFET device 200Aand PFET device 200B.

Referring to FIGS. 1 and 4A-4B, the method 1000 proceeds to step 1008 bydepositing a liner 405 over the substrate 210 and then filling in thetrench 230 with a dielectric layer 410 in both of the NFET 200A and thePFET 200B. First, the patterned OHM layer 310 is removed by an etchingprocess, such as a selective wet etch. In the present embodiment, theliner 405 is then deposited over the substrate 210, includingconformably wrapping over the first and second fin structures 220 and330. The liner 405 may include silicon nitride, silicon oxynitride,aluminum oxide, or other suitable materials. In one embodiment, theliner 405 is deposited by ALD to achieve adequate film coverage ofwrapping over the first and second fin structures 220 and 330.Alternatively, the liner 405 may be deposited by CVD, physical vapordeposition (PVD), or other suitable techniques. In the presentembodiment, the liner 405 is designed to be a buffer layer to preventthe second semiconductor material layer 214 be oxidized further in thedownstream or later processed and a barrier of out-diffusion of thesecond semiconductor material layer 214, which will be described indetail below.

The dielectric layer 410 is deposited over the liner 405 in thesubstrate 210, including filling in the trench 230, in both of the NFET200A and the PFET 200B. The dielectric layer 410 may include siliconoxide, silicon nitride, silicon oxynitride, spin-on-glass,spin-on-polymer, or other suitable materials, or combinations thereof.The dielectric layer 410 may be deposited by CVD, physical vapordeposition (PVD), ALD, thermal oxidation, spin-on coating, or othersuitable techniques, or a combination thereof. As has been mentionedpreviously, having the liner 405 cover the first and second finstructures 220 and 330, it provides a buffer to adverse impacts inducedduring the formation of the dielectric layer 410, such as in thermalcuring process for the dielectric layer 410.

A CMP process may be performed thereafter to remove excessive liner 405and the dielectric layer 410, as well as the FHM 222 and planarize thetop surface of the NFET device 200A and the PFET device 200B.

Referring to FIGS. 1 and 5A-5B, the method 1000 proceeds to step 1010 byrecessing the liner 405 and the dielectric layer 410 in both of the NFETdevice 200A and the PFET device 200B. The liner 405 and the dielectriclayer 410 are recessed by proper etching processes, such as a selectivewet etch, a selective dry etch, or a combination thereof. Alternatively,the liner 405 and the dielectric layer 410 are recessed through apatterned photoresist layer formed over the NFET device 200A and thePFET device 200B. In present embodiment, the recessing processes arecontrolled to fully expose the third semiconductor layer 216 in bothNFET device 200A and PFET device 200B.

Referring to FIGS. 1 and 6A-6B, the method 1000 proceeds to step 1012 bywrapping over the exposed third semiconductor material layer 216 in thefirst and second fin structures, 220 and 330 by a fourth semiconductormaterial layer 420 and an oxide capping layer 425 over the fourthsemiconductor material layer 420. In one embodiment, the fourthsemiconductor material layer 420 includes a Ge layer while the thirdsemiconductor material layer includes Si layer. In another embodiment,the fourth semiconductor material layer 420 includes SiGe layer whilethe third semiconductor material layer includes Si layer. The fourthsemiconductor material layer 420 and the oxide capping layer 425 may bedeposited by CVD, ALD, PVD, or other suitable processes.

Referring to FIGS. 1 and 7A-7B, the method 1000 proceeds to step 1014 byperforming a high temperature anneal to condense Ge to form Ge features430 as the upper portion of the first and second fin structures, 220 and330. In one embodiment, the temperature range is from about 800° C. toabout 1100° C. In the present embodiment, the third semiconductormaterial layer 216 is Si layer and the fourth semiconductor materiallayer 420 is Ge layer, or SiGe layer. During the high temperatureanneal, Ge condenses from the Ge (or the SiGe) layer 420 to concentratein a middle section 435 of the upper portion, while silicon oxide layeris formed an as outer layer 436 of the upper portion of the first andsecond fin structures, 220 and 330. In the present embodiment, the hightemperature annealing process is controlled to have the middle section435 of the upper portion be pure Ge feature 430. After the annealprocess, the silicon oxide outer layer 436 is removed by a suitableetching process, such as a selective wet etch. Therefore, the Ge feature430 replaced the third semiconductor material layer 216 as the upperportions of the first and second fin structures, 220 and 330, referredto as a third and a fourth fin structures, 440 and 445, respectively, asshown in FIGS. 7C and 7D. The Ge feature 430 formed by condensing Ge ina high temperature anneal provides advantage of low epitaxial defects.

In some embodiments, the FinFET device 200 includes source/drain (S/D)regions and gate regions. In furtherance of the embodiment, one of theS/D regions is a source region, and another of the S/D regions is adrain region. The S/D regions are separated by the gate region. For thesake of clarity to better description, the S/D regions and the gateregions in the NFET device 200A are referred to as a first S/D regions450A and a first gate regions 460A; the S/D regions and the gate regionsin the PFET device 200B are referred to as a second S/D regions 450B anda second gate regions 460B.

Referring to FIGS. 1 and 8A-8B, the method 1000 proceeds to step 1016 byforming a gate stack 510 and sidewall spacers 520 on sidewalls of thegate stack 510, in the first and second gate regions, 460A and 460B. Inone embodiment using a gate-last process, the gate stack 510 is a dummygate and will be replaced by the final gate stack at a subsequent stage.Particularly, the dummy gate stacks 510 are to be replaced later by ahigh-k dielectric layer (HK) and metal gate electrode (MG) after highthermal temperature processes, such as thermal annealing for S/Dactivation during the sources/drains formation.

In one embodiment, a dummy dielectric layer 505 is deposited over thesubstrate 210, including wrapping over the third and fourth finstructures, 430 and 440. The dummy dielectric layer 505 is designed toprotect the third and fourth fin structures, 440 and 445 during asubsequent process of forming dummy gate stacks, which will be describedlater. The dummy dielectric layer 505 may be deposited by ALD, CVD, PVDand other suitable techniques. In one embodiment, the dummy dielectriclayer 505 includes silicon oxide.

The dummy gate stack 510 is formed over the substrate 210 and ispartially disposed over the fourth fin structure 445 in the first gateregion 460A and the third fin structure 440 in the second gate region460B. In one embodiment, the dummy gate stack 510 includes a dielectriclayer 512, an electrode layer 514 and a gate hard mask (GHM) 516. Thedummy gate stack 510 is formed by a suitable procedure includingdeposition and patterning. The patterning process further includeslithography and etching. In various examples, the deposition includesCVD, physical vapor deposition (PVD), ALD, thermal oxidation, othersuitable techniques, or a combination thereof. The lithography processincludes photoresist (or resist) coating (e.g., spin-on coating), softbaking, mask aligning, exposure, post-exposure baking, developing thephotoresist, rinsing, drying (e.g., hard baking), other suitableprocesses, and/or combinations thereof. The etching process includes dryetching, wet etching, and/or other etching methods (e.g., reactive ionetching).

The dielectric layer 512 includes silicon oxide. Alternatively oradditionally, the dielectric layer 512 may include silicon nitride, ahigh-k dielectric material or other suitable material. The electrodelayer 514 may include polycrystalline silicon (polysilicon). The GHM 516includes a suitable dielectric material, such as silicon nitride,silicon oxynitride or silicon carbide. The sidewall spacers 520 mayinclude a dielectric material such as silicon oxide, silicon nitride,silicon carbide, silicon oxynitride, or combinations thereof. Thesidewall spacers 520 may include a multiple layers. Typical formationmethods for the sidewall spacers 520 include depositing a dielectricmaterial over the gate stack 510 and then anisotropically etching backthe dielectric material. The etching back process may include amultiple-step etching to gain etch selectivity, flexibility and desiredoveretch control.

Referring to FIGS. 1 and 9A-9B, the method 1000 proceeds to step 1018 byforming a first S/D features 610A in the first S/D regions 450A and asecond S/D features 610B in the second S/D regions 450B. In oneembodiment, a portion of the upper portion of the fourth fin structures445 in the first S/D region 450A and a portion of the upper portion ofthe third fin structures 440 in the second S/D region 450B are recessed.The recessing process is controlled to have a portion of the Ge feature430 remain in the third and fourth fin structures, 440 and 445. Thefirst S/D features 610A and the second S/D features 610B are thenepitaxially grow on the recessed third and fourth fin structures, 440and 450, in the first and second S/D regions 450A and 450B,respectively. The first and the second S/D features, 610A and 610B,include Ge, Si, GaAs, AlGaAs, SiGe, GaAsP, or other suitable material.The first and the second S/D features, 610A and 610B, may be formed byone or more epitaxy or epitaxial (epi) processes. The first and thesecond S/D features, 610A and 610B, may also be doped, such as beingin-situ doped during the epi processes. Alternatively, the first and thesecond S/D features, 610A and 610B, are not in-situ doped andimplantation processes (i.e., a junction implant process) are performedto dope the first and the second S/D features, 610A and 610B.

In one embodiment, the first S/D features 610A is formed by theepitaxially grown SiGe layer doped with phosphorous to form SiGe:P S/Dfeatures. While the second S/D features 610B is formed by theepitaxially grown GeSn layer doped with boron to form GeSnB S/Dfeatures.

Referring to FIGS. 1 and 10A-10B, the method 1000 proceeds to step 1020by forming an interlayer dielectric (ILD) layer 720 on the substrate 210between the gaps of the dummy gate stacks 510. The ILD layer 720includes silicon oxide, silicon oxynitride, low k dielectric material orother suitable dielectric materials. The ILD layer 720 may include asingle layer or alternative multiple layers. The ILD layer 720 is formedby a suitable technique, such as CVD, ALD and spin-on (SOG). A chemicalmechanical polishing (CMP) process may be performed thereafter to removeexcessive ILD layer 720 and planarize the top surface of the SRAM FinFETdevice 200.

Referring also to FIGS. 1 and 10A-10B, the method 100 proceeds to step1022 by removing the dummy gate stacks 510 in the first gate region 460Ato form one or more first gate trench 810A and in the second gate region460B to form one or more second gate trench 810B. The upper portion ofthe second fin structure 320 is exposed in the first gate trench 810Aand the upper portion of the third fin structure 440 is exposed in thesecond gate trench 810B. The dummy gate stacks 510 are removed by anetch process (such as selective wet etch or selective dry etch) designedto have an adequate etch selectivity with respect to the thirdsemiconductor material layer 216 in the first gate trench 810A and thefourth semiconductor material layer 445 in the second gate trench 810B.The etch process may include one or more etch steps with respectiveetchants. The gate hard mask layer 516 and the spacers 520 are removedas well. Alternatively, the dummy gate stack 510 may be removed by aseries of processes including photolithography patterning and etchingprocess.

Referring to FIGS. 1 and 11A-11B, the method 1000 proceeds to step 1024by forming a first and a second high-k/metal gate (HK/MG) stacks, 910Aand 910B, over the substrate 210, including wrapping over a portion ofthe fourth fin structures 445 in the first gate trench 810A and aportion of the third fin structure 440 in the second gate trench 810B,respectively. The first and the second HK/MG stack, 910A and 910B,include gate dielectric layer and gate electrode on the gate dielectric.In one embodiment, the gate dielectric layer includes a dielectricmaterial layer having a high dielectric constant (HK dielectriclayer-greater than that of the thermal silicon oxide in the presentembodiment) and the gate electrode includes metal, metal alloy or metalsilicide. The formation of the first and the second HK/MG stacks, 910Aand 910B, includes depositions to form various gate materials and a CMPprocess to remove the excessive gate materials and planarize the topsurface of the NFET device 200A and the PFET device 200B.

In one embodiment, the gate dielectric layer includes an interfaciallayer (IL) deposited by a suitable method, such as atomic layerdeposition (ALD), CVD, thermal oxidation or ozone oxidation. The ILincludes oxide, HfSiO and oxynitride. A HK dielectric layer is depositedon the IL by a suitable technique, such as ALD, CVD, metal-organic CVD(MOCVD), physical vapor deposition (PVD), other suitable technique, or acombination thereof. The HK dielectric layer may include LaO, AlO, ZrO,TiO, Ta2O5, Y2O3, SrTiO3 (STO), BaTiO3 (BTO), BaZrO, HfZrO, HfLaO,HfSiO, LaSiO, AlSiO, HfTaO, HfTiO, (Ba,Sr)TiO3 (BST), Al2O3, Si3N4,oxynitrides (SiON), or other suitable materials. The gate dielectriclayers wrap over the upper portion of the second fin structures 320 inthe first gate region 460A and the upper portion of the third finstructures 440 in the second gate region 460B.

A metal gate (MG) electrode may include a single layer or alternativelya multi-layer structure, such as various combinations of a metal layerwith a work function to enhance the device performance (work functionmetal layer), liner layer, wetting layer, adhesion layer and aconductive layer of metal, metal alloy or metal silicide). The MGelectrode may include Ti, Ag, Al, TiAlN, TaC, TaCN, TaSiN, Mn, Zr, TiN,TaN, Ru, Mo, Al, WN, Cu, W, any suitable materials or a combinationthereof. The MG electrode may be formed by ALD, PVD, CVD, or othersuitable process. The MG electrode may be formed separately for the NFET200A and the PFET 200B with different metal layers. A CMP process may beperformed to remove excessive MG electrode.

Referring to FIGS. 11C and 11D, in the NFET device 200A, the first gateregion 460A includes the first HM/MG 910A, which wraps over the upperportion of the fourth fin structure 445. The fourth fin structure 445includes the Ge feature 430 as its upper portion, the semiconductoroxide layer 324 as its middle portion, and the first semiconductormaterial layer 212 as its bottom portion. Therefore, during forming thesemiconductor oxide layer 324 in the fourth fin structure 445, a properstrain is induced to the first gate region 460A and it will increaseelectron mobility in a channel region in the first gate region 460A. Theliner 405 covers sidewalls of the bottom and middle portion of thefourth fin structures 445. The semiconductor oxide layer 324 alsoisolates the Ge feature 430 from the first semiconductor material layer212 to avoid its adverse impacts. The first S/D region 450A includesSiGeP S/D features 610A over a recessed Ge feature 430, which providesan epitaxial seed layer.

Referring to FIGS. 11E and 11F, in the PFET device 200B, the second gateregion 460B includes the second HM/MG 910B, which wraps over the upperportion of the third fin structure 440. The third fin structure 440includes the Ge feature 430 as its upper portion, the SiGe layer 214 asits middle portion, and the first semiconductor material layer 212 asits bottom portion. The liner 405 covers sidewalls of the bottom andmiddle portion of the third fin structures 440. The second S/D region450B includes GeSnB S/D features 610B over a recessed Ge feature 430,which provides an epitaxial seed layer. Alternatively, the second S/Dregion 450B includes SiGeSn S/D features.

The disclosure also discusses several different embodiments of a FinFETdevice 200, as shown in FIGS. 12 . 13A-13B, 14A-14B, 15A-15B, 16A-16B,17A-17B and 18A-18D, manufactured according to a method 2000. Thepresent disclosure repeats reference numerals and/or letters in thevarious embodiments. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Referring to FIGS. 11 and 13A-13B, the method 2000 begins at step 2002by forming fifth fin structure 2220 and trenches 2230 in a substrate2210 in the NFET 200A and the PFET 200B. The substrate 2210 the secondsemiconductor material layer 214 over the first semiconductor materiallayer 212 and the patterned FHM 222. The fifth fin structure 22220 andthe trench 2230 are formed by produces such as lithography and etchprocesses. A formation of the fifth fin structures 2220 and the trenches2230 are similar in many respects to those discussed above the first finstructure 220 in association with FIG. 2 . A depth of the etchingprocess is controlled that a remaining of the second semiconductormaterial layer 214 has a first thickness t₁.

Referring to FIGS. 12 and 14A, the method 2000 proceeds to step 2004 byextending the depth of trench 2230 in the PFET 200B by removing aportion of second semiconductor material layer 214. As shown, after thetrenches 2230 in the PFET device 200B are extended (or recessed further)a portion of second semiconductor material layer 214 remains in the PFETdevice 200B and has a second thickness t₂. For the sake of clarity tobetter description, the fifth fin structures 2220 in the PFET arereferred to as a sixth fin structures 2234.

Additionally, step 2004 includes forming a second FHM 2235 over the NFETdevice 200A prior to extending the trenches 2230 in the PFET device200B. As shown in FIG. 14A, the second FHM 2235 wraps over the fifth finstructures 2220 of the NFET device 200A. The second FHM 2235 is similarin many respects to the FHM 222 discussed above in association with FIG.2 .

Referring to FIGS. 12 and 15A-15B, the method 2000 proceeds to step 2006by forming a third FHM 2240 over the substrate 2210 and recessing thetrenches 2230 further. The third FHM 2240 is formed in both of the NFETdevice 200A and the PFET device 200B, including wrapping over the fifthand sixth fin structures, 2220 and 2234. The third FHM 2240 is similarin many respects to the FHM 222 discussed above in association with FIG.2 . The trenches 2230 in both of the NFET device 200A and the PFETdevice 200B are recessed further to extend to the first semiconductormaterial layer 212. Therefore, a portion of the second semiconductormaterial layer 214 is exposed in the extended trench 2230 in both of theNFET device 200A and PFET device 200B.

Referring to FIGS. 12 and 16A-16B, the method 2000 proceeds to step 2008by converting the exposed second semiconductor material layer 214, inboth the NFET device 200A and PFET device 200B, into a semiconductoroxide layer 324. Step 2008 is similar in many respects to the step 1006of the method 1000 discussed above in association with FIGS. 3A-3B.After forming the semiconductor oxide layer 324, the third FHM 2240 isremoved by a suitable etch process.

Referring to FIG. 12 , the method 2000 proceeds to step 2010 bydepositing a liner 405 and then filling in the trench 230 with adielectric layer 410 over the substrate 210, in both of the NFET 200Aand the PFET 200B. The step 2010 is similar in many respects to the step1008 of the method 1000 discussed above in association with FIGS. 4A-4B.

Referring to FIGS. 12 and 17A-17B, the method 2000 proceeds to step 2012by recessing the liner 405 and the dielectric layer 410 in both of theNFET device 200A and the PFET device 200B. The step 2012 is similar inmany respects to the step 1010 of the method 1000. In the PFET device200B, the second semiconductor material layer 214 is partially exposed,which forms an upper portion of the sixth fin structure 2234, while theun-exposed second semiconductor material layer 214 forms an uppersection of a middle portion and the semiconductor oxide layer 324 formsa lower section of the middle portion and the first semiconductormaterial layer 212 forms a bottom portion. In the NFET device 200A, thesecond semiconductor material layer 214 is fully exposed, which forms anupper portion of a seven fin structure 2440 while the semiconductoroxide layer 324 forms a middle portion and the first semiconductormaterial layer 212 forms a bottom portion.

The S/D regions are separated by the gate region. For the sake ofclarity to better description, the S/D regions and the gate regions inthe NFET device 200A are referred to as the first S/D regions 450A andthe first gate regions 460A; the S/D regions and the gate regions in thePFET device 200B are referred to as the second S/D regions 450B and thesecond gate regions 460B.

Referring to FIG. 12 , the method 2000 proceeds to step 2014 by wrappingover the exposed second semiconductor material layer 214 in the sixthand seventh fin structures, 2234 and 2440, by the fourth semiconductormaterial layer 420 and an oxide capping layer 425 over the fourthsemiconductor material layer 420. The step 2014 is similar in manyrespects to the step 1012 of the method 1000 discussed above inassociation with FIGS. 6A-6B.

Referring to FIG. 12 , the method 2000 proceeds to step 2016 byperforming a high temperature anneal to form Ge features 430 as a centersection 435 and an oxide layer 436 as outer layers of the upper portionof the sixth and seventh fin structures, 2234 and 2440. The oxide outerlayers 436 are removed later by a proper etching process. The step 2016is similar in many respects to the step 1014 of the method 1000discussed above in association with FIGS. 7A-7D.

Referring to FIG. 12 , the method 2000 proceeds to step 2018 by forminga gate stack 510 and sidewall spacers 520 on sidewalls of the gate stack510, in the first and second gate regions, 460A and 460B. The step 2018is similar in many respects to the step 1016 of the method 1000discussed above in association with FIGS. 8A-8B.

Referring to FIG. 12 , the method 2000 proceeds to step 2020 by formingthe first S/D features 610A in the first S/D regions 450 A and thesecond S/D features 610B in the second S/D regions 450B. The step 2020is similar in many respects to the step 1018 of the method 1000discussed above in association with FIGS. 9A-9B.

Referring to FIG. 12 , the method 2000 proceeds to step 2022 by formingthe interlayer dielectric (ILD) layer 720 on the substrate 210 betweenthe gaps of the dummy gate stacks 510. The step 2022 is similar in manyrespects to the step 1020 of the method 1000 discussed above inassociation with FIGS. 10A-10B.

Referring to FIG. 12 , the method 2000 proceeds to step 2024 by removingthe dummy gate stacks 510 in the first gate region 460A to form one ormore first gate trench 810A and in the second gate region 460B to formone or more second gate trench 810B. The step 2024 is similar in manyrespects to the step 1022 of the method 1000 discussed above inassociation with FIGS. 10A-10B.

Referring to FIGS. 12 and 18A-18B, the method 2000 proceeds to step 2026by removing the dummy gate stacks 510 in the first gate region 460A toform one or more first gate trench 810A and in the second gate region460B to form one or more second gate trench 810B. The step 2026 issimilar in many respects to the step 1024 of the method 1000.

Referring to FIGS. 18C and 18D, in the PFET device 200B, the second gateregion 460B includes the second HM/MG 910B, which wraps over the upperportion of the sixth fin structure 2234. The sixth fin structure 2234includes the Ge feature 430 as its upper portion, the SiGe layer 214 asits upper section of the middle portion, the semiconductor oxide layer324 as its lower section of the middle portion, and the firstsemiconductor material layer 212 as its bottom portion. The liner 405covers sidewalls of the bottom and middle portion of the third finstructures 430. The SiGe layer 214 in the sixth fin structure 2234 (theupper section of the middle portion) provides a proper strain to thesecond gate region 460B to enhance channel mobility in a channel regionin the second gate region 460B. The semiconductor oxide layer 324 (thelower section of the middle portion) isolates the Ge feature 430 fromthe first semiconductor material layer 212 to avoid its adverse impacts.

Additional operations may be implemented before, during, and after themethod 100, and some operations described above may be replaced oreliminated for other embodiments of the method. For example, in oneembodiment, the step 2004 is eliminated. Therefore, the sixth finstructure 2440 in the PFET device 200B is as same as the seventh finstructure 2445 in the NFET device 200A.

Based on the above, the present disclosure offers fin structures for aFinFET device. The fin structures employ pure Ge feature, as its upperportion, formed by condensing Ge from SiGe layer during a hightemperature annealing to concentrate Ge to a center section of the upperportion. Instead of forming by an epitaxial growing, the Ge featureformed by condensing Ge provides advantages of low epi defects. The finstructures also employ a SiGeO layer to separate the Ge feature awayfrom a Si layer, a lower portion of the fin structure, to reduce adversesubstrate impact. In a PFET device, the fin structures employ a SiGelayer between the Ge feature and the SiGeO layer to provide reasonablecompressive channel strain. The fin structures also employ a thin SiGelayer as epitaxial seed layer for S/D feature formation. The finstructure demonstrates device performance improvements.

The present disclosure provides an embodiment of a semiconductor device.The device includes a first fin structure disposed over an n-type FinFET(NFET) region of a substrate. The first fin structure includes a silicon(Si) layer, a silicon germanium oxide (SiGeO) layer disposed over thesilicon layer and a germanium (Ge) feature disposed over the SiGeOlayer. The device also includes a second fin structure over thesubstrate in a p-type FinFET (PFET) region. The second fin structureincludes the silicon (Si) layer, a recessed silicon germanium oxide(SiGeO) layer disposed over the silicon layer, an epitaxial silicongermanium (SiGe) layer disposed over the recessed SiGeO layer and thegermanium (Ge) feature disposed over the epitaxial SiGe layer.

The present disclosure also provides another embodiment of a fin-likefield-effect transistor (FinFET) device. The device includes a substratehaving an n-type FinFET (NFET) and a p-type FinFET (PFET) region. Thedevice also includes a first fin structure over the substrate in theNFET region. The first fin structure includes a germanium (Ge) layer asits upper portion, a silicon germanium oxide (SiGeO) layer as its middleportion and a silicon (Si) layer as its bottom portion. The device alsoincludes a second fin structure over the substrate in the PFET region.The second fin structure includes the germanium (Ge) layer as its upperportion, an epitaxial silicon germanium (SiGe) layer as its middleportion and the silicon (Si) layer as its bottom portion. The devicealso includes a high-k (HK)/metal gate (MG) stack over the substrate inthe NFET region, including wrapping over the upper portion of a portionof the first fin structure, a first source/drain (S/D) features,separated by the HK/MG stack, over the recessed upper portion of thefirst fin structure, the high-k (HK)/metal gate (MG) stack over thesubstrate in the PFET region, including wrapping over the upper portionof a portion of the second fin structure, a second source/drain (S/D)features, separated by the HK/MG stack, over the recessed upper portionof the second fin structure.

The present disclosure also provides a method for fabricating a FinFET.The method includes providing a fin structure over a substrate. The finstructure includes a first semiconductor material layer as its bottomportion, a semiconductor oxide layer as its middle portion and a thirdepitaxial semiconductor material layer as its upper portion. The methodalso includes depositing germanium-containing semiconductor materiallayer over the fin structure, depositing an oxide layer over thegermanium-containing semiconductor material layer, applying a hightemperature annealing to concentrate germanium (Ge) in a center portionof the upper portion and semiconductor oxide in an outer portion of theupper portion of the fin structure and removing the semiconductor oxideof the outer portion of the upper portion of the fin structure.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A device, comprising: a semiconductor layer; anoxide disposed over the semiconductor layer; a dielectric liner disposedon sidewalls of the oxide and on sidewalls of the semiconductor layer; asemiconductor component disposed over the oxide, wherein thesemiconductor layer and the semiconductor component have differentmaterial compositions, wherein an upper surface of the dielectric lineris disposed below an upper surface of the semiconductor component; and agate structure at least partially wrapping around the semiconductorcomponent.
 2. The device of claim 1, wherein: the semiconductor layercontains a first type of semiconductor element; the semiconductorcomponent contains a second type of semiconductor element; and the oxidecontains the first type of semiconductor element and the second type ofsemiconductor element.
 3. The device of claim 2, wherein: thesemiconductor layer contains silicon; the semiconductor componentcontains germanium; and the oxide contains silicon germanium oxide. 4.The device of claim 1, wherein: the semiconductor layer includes anupwardly protruding portion; and the oxide is disposed on the upwardlyprotruding portion.
 5. The device of claim 1, wherein the dielectricliner includes silicon nitride, silicon oxynitride, or aluminum oxide.6. The device of claim 1, further comprising: a dielectric componentdisposed between the semiconductor layer and the gate structure.
 7. Thedevice of claim 6, wherein the dielectric component is disposed onsidewalls of the dielectric liner.
 8. The device of claim 1, wherein abottom surface of the gate structure is disposed over a top surface ofthe oxide.
 9. The device of claim 1, wherein the device is a part of an-type FinFET.
 10. A device, comprising: a first semiconductor layerthat contains a first type of semiconductor material; a secondsemiconductor layer disposed over the first semiconductor layer, whereinthe second semiconductor layer contains the first type of semiconductormaterial and a second type of semiconductor material different from thefirst type of semiconductor material; a third semiconductor layerdisposed over the second semiconductor layer, wherein the thirdsemiconductor layer contains the second type of semiconductor material;a dielectric liner disposed on at least side surfaces of the secondsemiconductor layer; and a gate structure at least partially wrappingaround the third semiconductor layer; wherein: the second semiconductorlayer is in direct contact with the first semiconductor layer; or thethird semiconductor layer is in direct contact with the secondsemiconductor layer.
 11. The device of claim 10, wherein: the firstsemiconductor layer contains silicon; the second semiconductor layercontains silicon germanium; and the third semiconductor layer containsgermanium.
 12. The device of claim 10, wherein: the first semiconductorlayer includes an upwardly protruding portion; and the dielectric lineris further disposed on sidewalls of the upwardly protruding portion butnot on sidewalls of the third semiconductor layer.
 13. The device ofclaim 12, wherein the dielectric liner is disposed below a bottomsurface of the third semiconductor layer and below a bottom surface ofthe gate structure.
 14. The device of claim 10, further comprising: adielectric component disposed between the first semiconductor layer andthe gate structure.
 15. The device of claim 10, wherein a bottommostsurface of the gate structure is disposed over a top surface of thesecond semiconductor layer.
 16. The device of claim 10, wherein thedevice is a part of a p-type FinFET.
 17. The device of claim 10, whereinthe first semiconductor layer is wider than the second semiconductorlayer and the third semiconductor layer.
 18. A device, comprising: ann-type FinFET (NFET) that includes: a first semiconductor layer; anoxide disposed over the first semiconductor layer; a first dielectriccomponent disposed on sidewalls of the oxide; a second semiconductorlayer disposed over the oxide, wherein the first semiconductor layer andthe second semiconductor layer have different material compositions,wherein a bottom surface of the second semiconductor layer is disposedover a top surface of the first dielectric component; and a first gatestructure that at least partially wraps around the second semiconductorlayer; and a p-type FinFET (PFET) that includes: a third semiconductorlayer, wherein the third semiconductor layer has a same materialcomposition as the first semiconductor layer; a fourth semiconductorlayer, wherein the fourth semiconductor layer has a same materialcomposition as the second semiconductor layer; a fifth semiconductorlayer disposed between the third semiconductor layer and the fourthsemiconductor layer, wherein the fifth semiconductor layer contains acompound of the third semiconductor layer and the fourth semiconductorlayer; a second dielectric component disposed on sidewalls of the fifthsemiconductor layer, wherein a bottom surface of the fourthsemiconductor layer is disposed over a top surface of the seconddielectric component; and a second gate structure at least partiallywrapping around the fourth semiconductor layer.
 19. The device of claim18, wherein: the first semiconductor layer and the third semiconductorlayer each contains silicon; the second semiconductor layer and thefourth semiconductor layer each contains germanium; the fifthsemiconductor layer contains silicon germanium; and the oxide containssilicon germanium oxide.
 20. The device of claim 18, wherein the secondsemiconductor layer or the fifth semiconductor layer has anon-rectangular profile in a cross-sectional view.